The goal of this project is to produce monoclonal antibodies to "premalignant" cells during chemical hepatocarcinogenesis in rats to determine whether or not expression of these premalignant phenotypes can be used to provide a clearer understanding of carcinogenic progression. Putative premalignant cell populations are being isolated from rat livers early after exposure to 2-acetylaminofluorene in a choline-deficient diet. So far, conditions for treatment of livers with enzyme resistance that release cells have been worked out and preliminary isolation of cell using gradients at 1 g have been successful. Monoclonal antibodies will be produced to putative epitopes on "premalignant" cells that appear during experimental models of carcinogenesis and will be used to delineate lineages of progression of normal cells to cancer cells.